From patchwork Wed Sep 8 18:57:03 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Sebastian Andrzej Siewior X-Patchwork-Id: 12481709 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-13.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 746CFC433EF for ; Wed, 8 Sep 2021 19:04:53 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 35EE761074 for ; Wed, 8 Sep 2021 19:04:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 35EE761074 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 696A16E283; Wed, 8 Sep 2021 19:04:52 +0000 (UTC) X-Greylist: delayed 459 seconds by postgrey-1.36 at gabe; Wed, 08 Sep 2021 19:04:51 UTC Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by gabe.freedesktop.org (Postfix) with ESMTPS id 7EDA76E283; Wed, 8 Sep 2021 19:04:51 +0000 (UTC) From: Sebastian Andrzej Siewior DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1631127427; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6pw/RdHrc/CzkC23is54QzO2uIf7Wy7vdaWPzx8kuIk=; b=Dr5cIEnN4ZlXZuQQSARgL8tqun+7XF/7mNoC+c7ICPQnKRkE9pBwX86T90/ZPCg1zL6AlK YJsjSeFZjXJor8MN02Y4+8aE5OfMKobLG+a9jSdBx6N1GoEFgVs5av8obROCEoIvhqSg/v tvrH7LL/Hx5G9m0v/ZwUUaSz4oHTfgCpv64sSm9FXvYtef4UwfaGMTgjx+XT5EBKnfZgmQ nN+1v9QER5hEF03a4NgNigXPt1YDGktaNZx3tXAQlnC90vSiDwHUoVZ583ZjQv0dVa1S38 /YfGnOOxZz7gXnz47Vlwyhj8YZ9ItwTOwiWchknT33Eq6nrrTW1Pw24QTgVcCw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1631127427; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=6pw/RdHrc/CzkC23is54QzO2uIf7Wy7vdaWPzx8kuIk=; b=twWw5P+IrUvvgm2INwYv5u3UywepNToT+zB7iSdYKp4Bmc+wHtaAP1/1YI2ZfT75ovtBUc TMjE/Qc2PU9aRgCQ== To: dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org Cc: David Airlie , Daniel Vetter , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Chris Wilson , Peter Zijlstra , Thomas Gleixner , Clark Williams , Sebastian Andrzej Siewior Date: Wed, 8 Sep 2021 20:57:03 +0200 Message-Id: <20210908185703.2989414-3-bigeasy@linutronix.de> In-Reply-To: <20210908185703.2989414-1-bigeasy@linutronix.de> References: <20210908185703.2989414-1-bigeasy@linutronix.de> MIME-Version: 1.0 Subject: [Intel-gfx] [RFC PATCH 2/2] drm/i915/gt: Use spin_lock_irq() instead of local_irq_disable() + spin_lock() X-BeenThere: intel-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Intel graphics driver community testing & development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: intel-gfx-bounces@lists.freedesktop.org Sender: "Intel-gfx" execlists_dequeue() is invoked from a function which uses local_irq_disable() to disable interrupts so the spin_lock() behaves like spin_lock_irq(). This breaks PREEMPT_RT because local_irq_disable() + spin_lock() is not the same as spin_lock_irq(). execlists_dequeue_irq() and execlists_dequeue() has each one caller only. If intel_engine_cs::active::lock is acquired and released with the _irq suffix then it behaves almost as if execlists_dequeue() would be invoked with disabled interrupts. The difference is the last part of the function which is then invoked with enabled interrupts. I can't tell if this makes a difference. From looking at it, it might work to move the last unlock at the end of the function as I didn't find anything that would acquire the lock again. Reported-by: Clark Williams Signed-off-by: Sebastian Andrzej Siewior Reviewed-by: Maarten Lankhorst --- .../drm/i915/gt/intel_execlists_submission.c | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-) diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c index fc77592d88a96..2ec1dd352960b 100644 --- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c +++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c @@ -1265,7 +1265,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine) * and context switches) submission. */ - spin_lock(&engine->active.lock); + spin_lock_irq(&engine->active.lock); /* * If the queue is higher priority than the last @@ -1365,7 +1365,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine) * Even if ELSP[1] is occupied and not worthy * of timeslices, our queue might be. */ - spin_unlock(&engine->active.lock); + spin_unlock_irq(&engine->active.lock); return; } } @@ -1391,7 +1391,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine) if (last && !can_merge_rq(last, rq)) { spin_unlock(&ve->base.active.lock); - spin_unlock(&engine->active.lock); + spin_unlock_irq(&engine->active.lock); return; /* leave this for another sibling */ } @@ -1552,7 +1552,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine) * interrupt for secondary ports). */ execlists->queue_priority_hint = queue_prio(execlists); - spin_unlock(&engine->active.lock); + spin_unlock_irq(&engine->active.lock); /* * We can skip poking the HW if we ended up with exactly the same set @@ -1578,13 +1578,6 @@ static void execlists_dequeue(struct intel_engine_cs *engine) } } -static void execlists_dequeue_irq(struct intel_engine_cs *engine) -{ - local_irq_disable(); /* Suspend interrupts across request submission */ - execlists_dequeue(engine); - local_irq_enable(); /* flush irq_work (e.g. breadcrumb enabling) */ -} - static void clear_ports(struct i915_request **ports, int count) { memset_p((void **)ports, NULL, count); @@ -2377,7 +2370,7 @@ static void execlists_submission_tasklet(struct tasklet_struct *t) } if (!engine->execlists.pending[0]) { - execlists_dequeue_irq(engine); + execlists_dequeue(engine); start_timeslice(engine); }